Recently, various types of nonvolatile memories such as electrically programmable and erasable ROMs (flash memories) have been developed. The NOR type flash memory, which is a typical nonvolatile memory, is excellent in random access, as compared to the NAND type, and is mainly used to store a program for operating electronic devices. The NOR flash memory may be grouped into a boot type memory and a uniform type memory. The boot type memory has a small storage area (hereafter, boot area) in addition to the main storage area. The boot area stores data or a program that is read before the main storage area is accessed. The uniform type memory is not equipped with the boot area.
Japanese Patent Application Publication No. 2001-243781 (Document 1) discloses a semiconductor device that has a second storage area in addition to a first main storage area. By logically replacing a part of the first main storage area with a part of the second storage area in the same column, the address of the second storage area can be selected efficiently. Japanese Patent Application Publication No. 2000-268584 (Document 2) discloses a nonvolatile memory in which the nonvolatile memory should be shipped as a flash memory (capable of erasing and rewriting data) or a one time memory (not capable of erasing and erasing data) by the a manufacturer of an electronic device equipped with the memory. Japanese Patent Application Publication No. 2005-85398 (Document 3) discloses a nonvolatile memory having limited access to protection information under a certain condition. The protection information contains information that permits or inhibits writing, reading, and erasing data stored in the nonvolatile memory.
In recent years, semiconductor devices are required to have a reduced size and a higher integration density for the purpose of downsizing and manufacturing cost reduction of electronic devices.